Run-flat tyres are standard fitment on a growing number of new cars, particularly BMW, Mini and some Mercedes models. They look almost identical to conventional tyres but behave very differently in the event of a puncture.
How run-flat tyres work
Run-flat tyres have a reinforced sidewall that supports the weight of the car even when the tyre is completely flat. This allows you to continue driving at reduced speed (typically up to 50 mph) for a limited distance (typically up to 50 miles) after a puncture. The exact limits vary by manufacturer and are printed in your handbook.
Benefits
- No need to change a tyre at the roadside in unsafe or inconvenient conditions.
- Many run-flat equipped cars do not carry a spare tyre, saving weight and boot space.
- Reduced risk of losing control after a sudden deflation at speed.
Drawbacks
- They are more expensive than equivalent conventional tyres, often 20 to 50 percent more.
- Ride quality is typically firmer because of the stiffer sidewall.
- They cannot always be repaired after a puncture and often must be replaced entirely.
- If you switch from run-flats to conventional tyres, you will need to carry a spare or puncture repair kit.
How to tell if you have run-flat tyres
Look on the tyre sidewall for markings such as ROF (Dunlop), RFT, SSR (Continental), ZP (Michelin) or EMT. The vehicle handbook will also specify whether run-flats are fitted.
Mixing run-flat and conventional tyres
Do not mix run-flat and conventional tyres on the same axle. The handling difference between the two types can cause unpredictable behaviour, particularly in emergency manoeuvres. If replacing run-flats, replace the full axle.
At Steins Garage we can advise on the correct replacement tyre for your vehicle. Call 0131 554 3423 or contact us here.